1. Field of the Invention
The invention relates to automatic bleed valves for bleeding a gas from a pressurized liquid reservoir or for bleeding a liquid from a pressurized gas reservoir.
2. Brief Review of the Prior Art
One type of valve used for this purpose is shown in GB-A-2188561 and GB-A-2203520. In such valves, when bleeding a gas from a liquid, a housing is provided having a passage extending between a housing inlet and a housing outlet. The passage includes a bore in which a piston is slidably received with the piston including a capillary providing fluid communication between the inlet and the outlet. The piston is biased into an upstream position in which gas entering the inlet passes through the capillary to the outlet. If, however, liquid passes through the capillary, the pressure drop across the piston is increased and the piston moves to a downstream position in which the piston closes the outlet to prevent communication between the inlet and the outlet.
In general, such valves have been found to work satisfactorily. In certain systems, however, the reservoir, once bled and pressurized, can become partly depressurized due, for example, to high system flow rates. This resultant loss of pressure can result in the piston moving from the downstream position back into the upstream position with consequent loss of liquid and depressurization. Although such depressurization is normally of a transient nature, it could occur repeatedly before the system is shut down.